Spinal fixation system

ABSTRACT

A spinal fixation system includes a pedicle screw having a longitudinal axis. A fixation element is configured to connect the pedicle screw to at least one additional pedicle screw. A coupling mechanism includes a pedicle screw securing device adapted to secure the coupling mechanism to the pedicle screw and a fixation element securing device configured to secure the coupling mechanism to the fixation element. A fastening mechanism is configured to fasten both the pedicle screw securing device and the fixation element securing device. The fastening mechanism is located along the longitudinal axis of the pedicle screw.

This is a continuation of U.S. application Ser. No. 12/825,176, filed onJun. 28, 2010, which is a division of U.S. application Ser. No.11/071,604, filed on Mar. 3, 2005, now U.S. Pat. No. 7,744,635, which isa continuation-in-part of application Ser. No. 10/864,673, filed Jun. 9,2004, all of which are incorporated herein by reference in theirentireties.

FIELD OF THE INVENTION

The present invention relates to instrumentation and methods used in theperformance of spinal fusion procedures. In particular, the presentinvention relates to a spinal fixation system and related surgicalmethods.

BACKGROUND OF THE INVENTION

The spinal column is comprised of twenty-six interlocking vertebrae.These vertebrae are separated by disks. The spine provides load-bearingsupport for one-half of the body's mass and it protects the nerves ofthe spinal column. The disks provide shock absorption and facilitate thebending of the spine.

The combination of the vertebrae and disks at each vertebral segmentallows for motion of the spine, in particular, flexing, rotation, andextension. The motion and support functions of the spine, in combinationwith the many interlocking parts and nerve roots associated with thespinal column can result in back pain due to various reasons. Such backpain may result from the degeneration of disks due to age, disease, orinjury. Further, vertebral bodies may be compromised due to disease ordefect, such as a tumor, or injury, such as fracture.

Spinal fusion or fixation surgery is one way to treat back pain.Further, spinal fusion or fixation may be used to correct an abnormalcurvature of the spine or stabilize the spine due to injury or diseaseaffecting one or more disks or vertebrae. In a spinal fusion procedure,two or more adjacent vertebrae in the spine are fused together. Thefusion is typically accomplished by the utilization of spinalinstrumentation including pedicle screws and associated rods or platesused to mechanically fix the vertebrae together. Pedicle screws aretypically used in spinal fusion surgery because the pedicle serves as astrong mechanical attachment point to the spine. Bone graft material maybe utilized to aid in the creation of bone structure between the fusedvertebrae to create a single bone.

Spinal fixation components vary depending on the system being utilizedbut typically include pedicle screws that are inserted through thepedicle and into the vertebral body. The pedicle screws are attached toone another by a linking device, such as a rod or plate, that extendsvertically along the row of pedicle screws that are inserted. Severalcoupling systems are known in the art that are used for coupling thepedicle screws to the linking device, which is oriented parallel to thespinal column. Typically two columns of pedicle screws and linkingdevices are used, one on each side of the spinal column. Afterinstallation, the two linking devices may be attached to one another toprovide additional stabilization of that portion of the spine. As analternative or in addition to pedicle screws, spinal hooks may be used,each spinal hook being coupled to a vertebra via a portion of thevertebral arch.

Because of anatomical variations, the pedicle screws that are fixed toone another in a spinal fusion procedure may not be in longitudinalalignment with one another. Accordingly, spinal fixation systems,whether utilizing a rod or a plate, strive to allow some variability inthe placement of the pedicle screws while still accomplishing the goalof fixation with a single rod or plate along the pedicle screws.

One challenge associated with the design of a spinal fixation system isthe connection between the pedicle screws and the linking device.Ideally, the number of components involved should be minimized,especially the number of components that must be threaded together (suchas nuts and rods) in order to ease the assembly process and minimize theoverall time of the surgical procedure.

There is also a need for a spinal fixation system that may be utilizedwith a minimally invasive surgical approach, such as one that utilizessmaller access apertures or ports rather than a large incision along theentire portion of the spine being treated. A spinal fixation system thataddresses the needs for a minimally invasive approach may also addressthe desire to utilize bone graft material along the fixation site toenhance bony in-growth.

Further, there is a need for a spinal fixation system that not onlyutilizes fewer components but that requires fewer steps for assemblyonto the spine, thus shortening the overall time of the surgicalprocedure.

It would be desirable to provide a system and/or method that providesone or more of these or other advantageous features or addresses one ormore of the above-identified needs. Other features and advantages willbe made apparent from the present specification. The teachings disclosedextend to those embodiments that fall within the scope of the appendedclaims, regardless of whether they accomplish one or more of theabove-identified needs.

SUMMARY OF THE INVENTION

The invention relates to a spinal fixation system having a pedicle screwwith a longitudinal axis and a fixation element configured to connectthe pedicle screw to at least one additional pedicle screw. A couplingmechanism includes a pedicle screw securing device adapted to secure thecoupling mechanism to the pedicle screw and a fixation element securingdevice configured to secure the coupling mechanism to the fixationelement. A fastening mechanism is configured to fasten both the pediclescrew securing device and the fixation element securing device, thefastening mechanism located along the longitudinal axis of the pediclescrew.

The invention further relates to a spinal fixation system having apedicle screw and a fixation element configured to connect the pediclescrew to at least one additional pedicle screw. A coupling mechanismincludes a collet adapted to secure the coupling mechanism to thepedicle screw and a fixation element securing device configured tosecure the coupling mechanism to the fixation element. Rotation of thecollet fastens both the collet and the fixation element securing device.

The invention further relates to a spinal fixation system having apedicle screw with a longitudinal axis and a fixation element configuredto connect the pedicle screw to at least one additional pedicle screw.The spinal fixation system has a coupling mechanism with means forsecuring the coupling mechanism to the pedicle screw and means forsecuring the coupling mechanism to the fixation element. A fasteningmechanism is configured to fasten both the means for securing thecoupling mechanism to the pedicle screw and the means for securing thecoupling mechanism to the fixation element, the fastening mechanismlocated along the longitudinal axis of the pedicle screw.

The invention further relates to a spinal fixation system having apedicle screw and a fixation rod configured to connect the pedicle screwto at least one additional pedicle screw. A coupling mechanism includesa pedicle screw securing device adapted to secure the coupling mechanismto the pedicle screw, the pedicle screw securing device having a firstbase, a first loop configured to receive the pedicle screw, and a firsttightening device configured to secure the pedicle screw between thefirst loop and the first base. The coupling mechanism further includes arod securing device configured to secure the coupling mechanism to therod, the rod securing device having a second base, a second loopconfigured to receive the rod, and a second tightening device configuredto secure the rod between the second loop and the second base.

The invention is capable of other embodiments and of being practiced orbeing carried out in various ways. Alternative exemplary embodimentsrelate to other features and combinations of features as may begenerally recited in the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will become more fully understood from the followingdetailed description, taken in conjunction with the accompanyingdrawings, wherein like reference numerals refer to like elements, inwhich:

FIG. 1 is a perspective view of a spinal fixation system;

FIG. 2 is an exploded perspective view of the spinal fixation system ofFIG. 1;

FIG. 3 is a sectional view of the spinal fixation system of FIG. 1 takengenerally along line 3-3 of FIG. 1;

FIG. 4 is a perspective view of the spinal fixation system of FIG. 1connected to a spine;

FIG. 5 is a perspective view of a spinal fixation system connected to aspine;

FIG. 6 is an exploded perspective view of the spinal fixation system ofFIG. 5;

FIG. 7 is a sectional view of the spinal fixation system of FIG. 5 takengenerally along line 7-7 of FIG. 5;

FIG. 8 is a perspective view of the spinal fixation system of FIG. 5connected to a spine;

FIG. 9 is a perspective view of a spinal fixation system;

FIG. 10 is an exploded perspective view of the spinal fixation system ofFIG. 9;

FIG. 11 is a sectional view of the spinal fixation system of FIG. 9taken generally along line 11-11 of FIG. 9;

FIG. 12 is a perspective view of the spinal fixation system of FIG. 9connected to a spine;

FIG. 13 is a perspective view of a spinal fixation system;

FIG. 14 is an exploded perspective view of the spinal fixation system ofFIG. 13;

FIG. 15 is a sectional view of the spinal fixation system of FIG. 13taken generally along line 15-15 of FIG. 13;

FIG. 16 is a perspective view of the spinal fixation system of FIG. 13connected to a spine;

FIG. 17 is a perspective view of a pedicle screw and drill assembly;

FIG. 18 is a perspective view of the pedicle screw and drill assembly ofFIG. 17 as assembled for use;

FIG. 19 is a sectional view of the pedicle screw and drill assembly ofFIG. 18;

FIG. 20 is a perspective view of the pedicle screw and drill assembly ofFIG. 18 positioned for use on a spine;

FIG. 21 is a perspective view of the pedicle screw and drill assembly ofFIG. 20 after connection of the pedicle screw to the spine;

FIG. 22 is a perspective view of a pedicle screw and associated drillassembly connected to a spine;

FIG. 23 is an exploded perspective view of the components of a spinalfixation system;

FIG. 24 is an exploded perspective view of a spinal fixation system;

FIG. 25 is a perspective view of the spinal fixation system of FIG. 24with the components assembled;

FIG. 26 is a perspective view of a bone graft implant;

FIG. 27 is a perspective view of a bone graft implant in use as part ofa spinal fixation system;

FIG. 28 is a perspective view of a spinal fixation system;

FIG. 29 is an exploded perspective view of the spinal fixation system ofFIG. 28;

FIG. 30 is a partial sectional view of the spinal fixation system ofFIG. 28 taken generally along line 30-30 of FIG. 28;

FIG. 31 is a partial sectional view of the spinal fixation system ofFIG. 28 showing the pedicle screw secured at an angle;

FIG. 32 is a perspective view of a spinal fixation system;

FIG. 33 is an exploded perspective view of the spinal fixation system ofFIG. 32;

FIG. 34 is a sectional view of the spinal fixation system of FIG. 32taken generally along line 34-34 of FIG. 32;

FIG. 35 is a partial perspective view of the spinal fixation system ofFIG. 32 taken generally along line 35-35 of FIG. 32;

FIG. 36 is a partial sectional view of the spinal fixation system ofFIG. 32 showing the pedicle screw secured at an angle;

FIG. 37 is a perspective view of a spinal fixation system;

FIG. 38 is an exploded perspective view of the spinal fixation system ofFIG. 37;

FIG. 39 is a partial sectional view of the spinal fixation system ofFIG. 37 showing the pedicle screw secured at an angle;

FIG. 40 is a perspective view of a spinal fixation system;

FIG. 41 is an exploded perspective view of the spinal fixation system ofFIG. 40; and

FIG. 42 is a partial sectional view of the spinal fixation system ofFIG. 40 taken generally along line 42-42 of FIG. 40.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Referring to FIG. 1, in an exemplary embodiment of the invention, aspinal fixation system includes a bone anchoring element or bone screw,shown as pedicle screw 10. The pedicle screw 10 is coupled to a fixationelement or linking device, shown as fixation plate 12, via a couplingmechanism 14. In use, the pedicle screw 10 may be inserted through apedicle and into a vertebra and linked to other pedicle screws by thefixation plate 12. The length of the fixation plate 12 is chosen toaccommodate the total distance between the pedicle screws that arelinked together.

Referring to FIG. 2, the pedicle screw 10 includes a threaded portion 16and a non-threaded upper portion, shown as post 18. A tip 20 may beconfigured to be self-drilling and a shoulder or flange 22 may extendfrom the screw 10 between the post 18 and threaded portion 16. At thetop of the post 18, an engagement mechanism for a screwdriver or drill,shown as recess 24, may be utilized. A receiver 26 includes a pair ofwall portions 28 that together form a U-shaped receiver sized to receivefixation plate 12. The internal side of wall portions 28 may be threadedto engage with other instrumentation. The wall portions 28 extendupwardly from base 30.

Further referring to FIG. 2, collar 32 has a threaded interior portionand a shoulder 34 that is sized to rest upon base 30. A collet 36includes a number of compressible arms 38 intended to engage withpedicle screw 10 upon assembly. A lower set screw 40 has a head 42 thatmay be configured to be grasped by a tool, such as the hex-headconfiguration shown in FIG. 2. A threaded portion 44 is configured toengage with the internal threads of the collar 32 during assembly. Apair of retaining rings 46, 48 engage either side of fixation plate 12,the lower retaining ring 46 resting upon collar 32 and the upperretaining ring 48 compressed between the fixation plate 12 and an upperset screw 50. The upper set screw 50 has a threaded portion 52 intendedto engage with the threaded interior side of wall portions 28 of thereceiver 26 upon assembly. The upper set screw 50 may have a headconfiguration designed to be engaged by a wrench or other tighteningtool.

Referring to FIG. 3, while an upper portion of the interior of collar 32is threaded to engage with lower set screw 40, the lower portion is notthreaded but has a tapered interior portion having a more narrowdiameter at the bottom of the collar 32. During assembly of the fixationsystem, the collar 32 is dropped into the receiver 26, the shoulder 34resting upon the base 30. Note that each of the components forming thecoupling mechanism has an interior channel or aperture configured toallow the components to be placed upon and encircle the post 18. Thecollet 36 is placed into collar 32, the outer diameter of the collet 36being greater along a portion of the longitudinal axis of collet 36 thanthe interior diameter of collar 32, as shown in FIG. 3. The lower setscrew 40 may then be threaded into collar 32, thus engaging collet 36and pushing collet 36 downward through the collar 32 until thecompressible arms 38 are forced to grip and be secured to post 18.Engagement of the post 18 by the collet 36 locks the collet 36 and theother components of the coupling mechanism into place relative to thepedicle screw 10 for fixation to the fixation plate 12.

Note that the collet 36 may be locked onto post 18 at any position alongthe longitudinal axis of post 18, affording flexibility in the placementof the coupling mechanism components. In other pedicle screwembodiments, the collet may engage with the threaded portion of thepedicle screw. The flexibility in placement of the collet is importantdue to the variability in placement of the pedicle screw 10 depending onthe anatomy of the patient's spine. Once the receiver 26, collar 32, andcollet 36 are locked into place onto pedicle screw 10, the fixationplate 12 may be linked to the pedicle screw 10 by placing retainer rings46, 48 over the post 18 on either side of the fixation plate 12 andlocking the fixation plate 12 into place by threading upper set screw 50into receiver 26 to complete the assembly.

Further referring to FIG. 3, the recess 24 extends into the pediclescrew 10 to create a keyed portion of a passage 54 that extends thelength of the pedicle screw 10. The keyed portion may serve as anengagement point for a driver as discussed above.

Referring to FIG. 4, the embodiment of the spinal fixation system shownin FIGS. 1-3 is shown installed into a patient's spine. In practice, thepedicle screws 10 may be individually installed prior to theinstallation of the fixation plate 12 across the multiple pedicle screws10. Note that the fixation plate 12 is centered upon the line of pediclescrews 10 as opposed to the offset configuration seen with otherfixation system embodiments.

Referring to FIG. 5, a fixation system in accordance with anotherembodiment of the invention is shown and includes a bone couplingelement or bone screw, shown as pedicle screw 100, a linking device,shown as fixation rod 102, and a coupling mechanism (generally shown ascoupling mechanism 104) used to connect the pedicle screw 100 andfixation rod 102 together. The fixation rod 102 provides similarfunctionality to the fixation plate 12.

Referring to FIG. 6, pedicle screw 100 includes a threaded portion 106and a non-threaded post 108. A recess 110 is provided at the top ofpedicle screw 100 in order to provide an engagement point for a drill orscrewdriver. In this embodiment as with other embodiments describedherein, the triangle-shaped recess is exemplary only and may takevarious forms such as a slot or a hexagonal recess depending on the typeof tool utilized for turning the pedicle screw. A receiver 112 includesa pair of wall portions 114 extending upwardly from base 116. A collar118 is integrally formed as part of the receiver 112. The U-shapedconfiguration of the upwardly extending wall portions 114 and base 116is suited to receive and be attached to fixation rod 102. A collet 120is sized to fit into the collar 118 and be pressed downward by a setscrew 122, the set screw 122 having a threaded portion 124 such that itmay be screwed into the collar 118. A nut 126 is sized to be connectedto a threaded portion 128 of the receiver 112.

Referring to FIG. 7, the fixation rod 102 is attached to the pediclescrew 100 by the various components of the coupling mechanism. Inparticular, the receiver 112 is first placed upon the post 108, followedby insertion of the collet 120 and the set screw 122 into the receiver112 and collar 118. Tightening the set screw 122 forces the collet 120downward through the narrowing passageway of the collar 118 such thatthe compressible arms of the collet 120 are forced inward to grip andfasten to the post 108 at the desired point on the post 108. Once thecollet 120 is secured onto the post 108, the receiver 112 is also fixedinto place and ready for placement of the fixation rod 102 into theU-shaped channel of the receiver 112, followed by the addition of thenut 126 to secure the fixation rod 102 into place, completing theinstallation of the fixation hardware for a particular vertebra.

Further referring to FIG. 7, prior to adding the coupling mechanism andfixation rod, the pedicle screw 100 is first installed into the vertebraby screwing the pedicle screw 100 into place, with the use of theself-drilling configuration of pedicle screw 100 or other installationmethods known in the art. Recess 110 may be used as the engagement pointfor the pedicle screw 100 for drilling the pedicle screw into the chosenvertebra. The pedicle screw 100 may be cannulated as shown by thepassage 130 extending the length of the pedicle screw 100 with anopening at both the proximal end and the distal end of the pedicle screw100.

Referring to FIG. 8, the spinal fixation system depicted in FIGS. 5-7 isshown installed into a patient's spine. Note that different pediclescrews 100 may protrude from the spine at different heights depending onanatomical variations that may affect how deep the pedicle screw 100 isdrilled into particular vertebra. Accordingly, the use of the collet 120that may engage the pedicle screw 100 at various heights is useful topermit the fixation rod 102 to be utilized in connecting the variouspedicle screws 100 together.

Referring to FIGS. 9-12, a spinal fixation system according to anotherembodiment of the invention is shown and includes a bone couplingelement, shown as pedicle screw 200, a linking device, shown as fixationplate 202, and a coupling mechanism, the components generally shown ascoupling mechanism 204.

Referring to FIG. 10, the pedicle screw 200 is similar to the pediclescrews described with respect to other embodiments of the invention, andincludes a threaded portion 206 and a non-threaded portion, shown aspost 208. A recess 210 provides an interface for a tool or drill used todrill the pedicle screw 200 through a pedicle and into a vertebral body.A collet 214 has an elongated design with an inner aperture designed tobe fitted over post 208, a set of compressible arms 216 designed toengage the pedicle screw 200, and a threaded portion 218. A collar 212is designed to interface with the compressible arms 216. A pair ofretaining rings 220, 222 provide an engagement point for the couplingmechanism with the fixation plate 202. A fastening device, shown as nut224, has threads configured to engage with the threaded portion 218 ofthe collet 214.

Referring to FIG. 11, in order to utilize the coupling mechanism toinstall the friction plate 202 to the pedicle screw 200, the collet 214,collar 212, and retaining ring 220 are placed over the post 208 afterinstallation of the pedicle screw 200 into the chosen vertebra. The post208 upon which the various components of the coupling mechanism areplaced provides a guide and retaining function during assembly of thecoupling mechanism to ease the attachment of the fixation plate 202.

After placement of the fixation plate 202 over the post 208, theretaining ring 222 and nut 224 are placed into position over thefixation plate 202. Tightening of the nut 224 performs two functions.First, the nut 224 engages the threads of the collet 214 and pulls thecompressible arms 216 up into the collar 212 in order to depress thecompressible arms 216 into the post 208, thereby locking the collet 214onto the pedicle screw 200. Further, the nut 224 locks the fixationplate 202 relative to the pedicle screw 200 by compressing the fixationplate 202 between the retaining rings 220, 222. A passage, shown aspassage 226 extends the length of the pedicle screw 200 generallyextending from the recess 210.

The embodiment of the invention shown in FIGS. 9-12 requires only onecomponent to be screwed into place, the nut 224, which connects both thefixation plate 202 and the collet 214 to the pedicle screw 200. The restof the components of the coupling mechanism 204 slide into place overthe post 208. Reducing the number of components that must be screwedtogether in the assembly of the spinal fixation system is advantageousas cross-threading of components that are screwed together is a problemencountered in surgery and reducing the number of components that mustbe screwed together addresses that issue. Further, only requiring onepair of components to be screwed together per pedicle screw may reducethe time necessary to assemble the spinal fixation system, therebyreducing the overall time required for the operation.

Referring to FIG. 12, the invention shown in FIGS. 9-11 is shown asinstalled into a spine, with two pedicle screws 200 shown for exemplarypurposes although a greater number of pedicle screws 200 may beutilized, depending on the number of vertebrae to be fixed to oneanother. The fixation plate 202 may be of various lengths depending onthe number of pedicle screws 200 used. Because the collet 214 may engagethe pedicle screw 200 at various points, variations in the heights ofthe installed pedicle screws 200 may be addressed in order to result ina continuous height of the fixation plate 202 by simply varying thepoints of engagement of the coupling mechanism 204 on different pediclescrews 200.

Referring to FIGS. 13-16, a spinal fixation system according to anotherembodiment of the invention includes a bone-coupling element, shown aspedicle screw 300, a fixation element or linking device, shown asfixation rod 302, and a coupling mechanism, generally shown as couplingmechanism 304.

Referring to FIG. 14, the pedicle screw 100 includes a threaded portion306 and a non-threaded portion shown as post 308. The threaded portion306 is bounded by a distal tip 310 and a flange 312. A recess 314extends into the post 308 for engagement by a tool or drill. A collet318 has an interior channel sized to fit over the post 308. The collet318 includes a threaded portion 322 and a number of compressible arms320. A collar 316 is sized to fit over the collet 318. A receiver forthe fixation rod 302 includes a pair of plates, shown as lower portion328 and upper portion 330. The plates are hinged so that the upperportion 330 is pivotally attached to the lower portion 328. The lowerportion 328 includes a hook 334 for engagement with the fixation rod 302and the upper portion 330 includes an engagement arm 332 that is used tolock the fixation rod 302 into place. A pair of retaining rings 324, 326are disposed on either side of the receiver and a fastening device,shown as nut 336, is configured to secure the entire coupling mechanismtogether by threading onto collet 318.

Referring to FIG. 15, the coupling mechanism is secured to the pediclescrew 300 in a similar fashion to that described with respect to theembodiment depicted in FIGS. 9-12 via the tightening of nut 336 ontocollet 318, thereby pulling the compressible arms 320 up into the collar316, thereby fixing the collet 318 into place at the selected heightupon pedicle screw 300. Engagement with the fixation rod 302 however ishandled differently by using the components of the receiver to attachthe coupling mechanism to the fixation rod 302 with the fixation rod 302offset from the longitudinal axis of the pedicle screw 300. Furtherreferring to FIG. 15, tightening the nut 336 onto the collet 318 notonly secures the collet 318 into place on the pedicle screw 300 but alsodrives the upper portion 330 downward toward the lower portion 328 untilthe engagement arm 332 engages the fixation rod 302 to fix the fixationrod 302 into place relative to the coupling mechanism and the pediclescrew 300. Accordingly, the fastening device or nut 336 performs twocoupling functions that require at least two fastening components inother designs. During assembly, the various components of the couplingmechanism are stacked onto the pedicle screw 300 using the post 308 as aguide after installing the pedicle screw 300 into the bone. Thecomponents of the receiver are configured to be installed on the post308 along a range of positions offset from the longitudinal axis of thepedicle screw 300 to allow for some variability in the angle of thepedicle screw 300 after installation into the chosen vertebra. Further,like the earlier described embodiments, the coupling mechanism may beadjusted along the longitudinal axis of the pedicle screw 300 to accountfor variability in the height of the installed pedicle screw 300.

Referring to FIG. 16, the spinal fixation system shown in FIGS. 13-15may be installed in the spine with the fixation rod 302 oriented oneither side of the pedicle screws 300 by changing the position of thereceiver lower portion 328 and upper portion 330. Although two pediclescrews 300 are shown as fixed by fixation rod 302, additional pediclescrews 300 may be installed in a line with a fixation rod 302 having theappropriate length to connect the pedicle screws 300.

Referring to FIGS. 17-22, in an exemplary embodiment of the invention, apedicle screw 400 may be used in conjunction with a driver, shown asdrill 414, and holding device 430. As in earlier described embodiments,the pedicle screw 400 includes a threaded portion 402, a non-threadedpost 404, a tip 406, a flange or ridge 410, and a recess 412. The drill414 includes a shaft 416 sized to fit within a passage 408 (see FIG.19), a portion having cutting edges 418, and a drill tip 420. Referringto FIGS. 3, 7, 11, and 15, the pedicle screws shown in variousembodiments of the invention are cannulated to include passages 54, 130,226, and 338 to accommodate drills such as drill 414. Accordingly, thedrill 414 may function as a drill and as a driver for turning the screw.The term “driver” is intended to generically refer to a drill or turningtool or a tool having both functions. A keyed segment 422 of the drillis shaped to lock into recess 412 so that when the drill 414 is rotated,the pedicle screw 400 is also rotated. An expanded segment 424 is sizedto rest upon the top of post 404, and has an outer diameter that is thesame as that of post 404 in a preferred embodiment. An upper keyedsegment 426 provides an interface for a drill or other turning tool usedto turn the drill 414 and the pedicle screw 400.

Further referring to FIG. 17, a holding device 430 is shown as having acylindrical shape and an attachment mechanism, shown as a number ofprongs 432, extending from the bottom of the holding device 430 andintended to snap over the ridge 410 to connect the holding device 430 tothe pedicle screw 400. Referring to FIG. 19, the top of the holdingdevice 430 may be shaped to engage expanded segment 424 to lock thedrill 414 into place in the pedicle screw 400.

Referring to FIG. 18, once assembled together, the pedicle screw 400,drill 414, and holding device 430 create an efficient tool for drillingthe pedicle screw into a selected vertebra. The drill tip 420 extendsfrom the distal opening of the passage in the pedicle screw at thepedicle screw tip 406 to aid in the insertion of the pedicle screw 400.The smaller diameter cutting edges 418 and sharp cutting tip 420 may bedesired by a surgeon when inserting the pedicle screw 400 to provide amore accurate placement and initial drilling point for the pedicle screw400, eliminating the necessity of first drilling a pilot hole andutilizing a guide wire to guide the pedicle screw. Inserting a separateguide wire with a separate drill bit requires additional steps in thesurgery and additional components, complicating and perhaps lengtheningthe overall surgery. The holding device 430 aids in the manipulation ofthe pedicle screw 400 and drill 414 by preventing the drill 414 fromdisengaging from the pedicle screw 400 during the insertion process.

Referring to FIG. 19, the drill 414 and holding device 430 may beassembled together with the pedicle screw 400 prior to connecting thepedicle screw 400 to the spine and may be assembled by sliding thecomponents together and snapping the holding device 430 onto the pediclescrew 400 without having to screw various components together.

Referring to FIG. 20, the assembled device depicted in FIG. 18 may beutilized to drill the pedicle screw 400 into a chosen location in thespine utilizing the drill 414 in combination with the pedicle screw 400.The drill tip 420 aids in selecting a precise location for drilling thehole for the pedicle screw 400.

Referring to FIG. 21, once the pedicle screw 400 has been screwed intothe vertebra, the holding device 430 may be removed from the pediclescrew 400 by disengaging the prongs 432, which in a preferred embodimentmay be disengaged by pulling the holding device 430 away from thepedicle screw 400. Referring to FIG. 22, once the holding device 430 hasbeen removed from the pedicle screw 400, the drill 414 remains. In apreferred embodiment, the drill may be removed from the pedicle screw400 by pulling the keyed segment 422 out of the recess 412. However, theuser may elect to leave the drill 414 in place (or replace the drill 414with another driver configured to be inserted into the passage 408)during assembly of the coupling mechanism as described below.

Referring to FIG. 23, the drill 414 may be utilized in conjunction witha pedicle screw after installation of the pedicle screw to aid in theinstallation of various coupling components. In the embodiment depictedin FIG. 23, the components of the coupling mechanism 304 shown in FIGS.13-16 are shown for exemplary purposes only. A similar approach may beutilized with the other coupling mechanisms and components shown withrespect to the spinal fixation systems described in other embodiments ofthe invention. The drill 414, including upper keyed segment 426 andexpanded segment 424, is sized to provide a guide for the couplingcomponents utilized to attach the pedicle screw 300 to the fixation rod302. Accordingly, after installation of the pedicle screw 300, a surgeonmay elect to leave the drill 414 in place and utilize the drill 414 toserve as a guide for installation of the collet 318, collar 316,retaining ring 324, receiver lower portion 328, and upper portion 330,retaining ring 326, and nut 336. Alternatively, the surgeon may removethe drill 414 and insert a similarly configured driver into the screw tofunction as the guide.

In a minimally invasive surgical approach, use of the drill 414 as aguide for the coupling components may be especially useful because asmall percutaneous aperture may be made for each installed pediclescrew, and the drill 414 may extend out of the patient's body to aid inplacement of the coupling components. Without the aid of the drill 414as a guide in minimally invasive surgical approaches, placement of thecomponents directly onto the post 308 may be difficult due to the smallsize of the percutaneous aperture and obstructed visual access.

Referring to FIG. 24, expanding on the concept presented in FIG. 23, thedrill 414 may be left in place in multiple pedicle screws 300 after theinstallation of each pedicle screw 300. Such an approach requires theuse of multiple drills 414 so that during a surgical operation, eachpedicle screw 300 may be installed with a separate drill 414, the drill414 left into place for installation of coupling components for eachpedicle screw 300. FIG. 24 depicts two pedicle screws 300 requiringcoupling components for exemplary purposes but the concept may beutilized with any number of pedicle screws.

Referring to FIG. 25, after the coupling components have been put intoplace and attached to the fixation rod 302, the individual drills 414may be removed by pulling the drills out of the pedicle screws, leavingthe installed components (including the pedicle screws 300) in place.One reason for the utilization of a separate drill 414 which isremovable from the installed fixation system is that the surgeon may notwish to utilize components of a fixation system that include apermanently installed sharp cutting tip.

Referring to FIGS. 26 and 27, in accordance with one embodiment of theinvention, the spinal fixation system includes a mechanism for insertingbone graft material as part of a spinal fusion procedure, shown as bonegraft implant 500. The bone graft implant 500 includes a reservoir,shown as a nylon or fiber mesh bag 502, having a pair of end caps 504. Anumber of apertures, shown as grommets 506, may be placed in the bag 502on both sides of the bag 502 to permit installation of the bag 502 overa number of pedicle screws. The bag 502 may be filled with a bone graftmaterial and utilized to enhance spinal fusion.

Referring to FIG. 27, in one embodiment, the bone graft implant 500 maybe placed over a number of pedicle screws 508 prior to installation of alinking device, shown as fixation plate 510, and the associated couplingmechanism. In the embodiment depicted in FIG. 27, the pedicle screws,fixation plate, and coupling mechanism are similar to the componentsshown in the spinal fixation system embodiment described above withrespect to FIGS. 9-12. In a surgical procedure, the pedicle screws 508may be installed into the selected vertebrae, followed by installationof the bone graft implant 500, which has already been filled with bonegraft material, over the posts of the pedicle screws 508. The grommets506 provide a mechanism for maintaining the placement of the bone graftimplant 500 in the proper location and also provides an effective guidemechanism where visual access is impaired because the grommets 506 maybe placed over the free posts of the pedicle screws 508 and glided intoposition along the pedicle screws. When a minimally invasive approach isused with a small access port for each individual pedicle screw, thebone graft implant 500 may be inserted into the patients body throughone aperture, with the placement of a grommet 506 over the post of thepedicle screw, and then threaded under the patient's skin up to the nextpedicle screw for placement of the next grommet, and so forth for thenumber of pedicle screws that are being utilized. A string may bethreaded between the adjacent pedicle screws to aid in the pulling ofthe bone graft implant 500 between the access ports.

Referring to FIGS. 28-31, a spinal fixation system according to anotherembodiment of the invention is shown and includes a bone couplingelement, shown as pedicle screw 600, a linking device or fixationelement, shown as fixation rod 602, and a coupling mechanism, generallyshown as coupling mechanism 604.

Referring to FIG. 29, the pedicle screw 600 is similar to the pediclescrews described with respect to other embodiments of the invention andincludes a threaded portion 606 and a non-threaded portion, shown aspost 608. Other pedicle screw designs may also be used with the couplingmechanism 604. A recess 610 provides an interface for a tool or drillused to drill the pedicle screw 600 through a pedicle and into avertebral body. Similar to the other pedicle screws described herein,passage 622 extends the length of the pedicle screw 600. A pedicle screwsecuring device, shown as collet 614, includes an internal aperturedesigned to be fitted over post 608, a set of compressible arms 616designed to engage the pedicle screw 600, and a threaded portion 618.Instead of the collet 614, the pedicle screw securing device may takeother forms such as a Morse Taper or a tongue and groove configuration.

Further referring to FIG. 29, the coupling mechanism includes a body 612having two passages, one sized to receive the fixation rod 602 and theother sized to receive the collet 614, pedicle screw 600, and anengagement or fastening device, shown as split ring 620. While the twopassages shown in FIG. 29 extend orthogonally to one another, the twopassages may extend in other directions relative to one another in otherembodiments of the invention. The two passages are connected by anaperture allowing the split ring 620 to act upon the fixation rod 602.In other embodiments, the split ring may be replaced by a cam or slidingpin. The split ring 620 includes interior threads configured to matewith the external threads of the collet 614. The collet 614 includes anengagement design at the top of the collet that is engaged by atightening tool, such as a wrench having an interlocking design, thatmay be used to rotate the collet 614 to secure the collet 614 into thesplit ring 620.

Referring to FIG. 30, in order to utilize the coupling mechanism 604 tocouple the fixation rod 602 to the pedicle screw 600, the collet 614,split ring 620, and body 612 are placed over the post 608 afterinstallation of the pedicle screw 600 into the chosen vertebra. Thevarious components of the coupling mechanism are slidable with respectto the fixation rod 602 and the post 608 prior to tightening to allowfor proper adjustment of the various components. Once the desiredplacement is achieved, the collet 614 may be screwed into the split ring620. In other embodiments, the collet may engage the fastening mechanismin different ways such as through the use of splines.

The split ring 620 acts as a fastening device by performing twofunctions. First, rotation of the collet 614 into the split ring 620forces the split ring 620 outward such that the outer surface of thesplit ring 620 engages the fixation rod 602, thus securing the fixationrod 602 with respect to the body 612, functioning as a fixation elementsecuring device. Second, the split ring 620 forces the compressible arms616 of the collet 614 onto the post 608, thus securing the pedicle screw600 to the body 612.

Further referring to FIGS. 28-31, the coupling mechanism 604 is securedto both the pedicle screw 600 and fixation rod 602 by the tightening ofone fastening mechanism, the collet 614. Accordingly, the design isintended to simplify the process of coupling the fixation rod 602 to thepedicle screw 600 by reducing the number of actions necessary toaccomplish this task. Further, the component that is acted upon toaccomplish the fastening of the coupling mechanism, the collet 614, iscentered along the longitudinal axis of the pedicle screw 600.

When installing a spinal fixation system utilizing minimally invasivesurgical techniques, a small percutaneous aperture may be opened in thepatient for installation of the various pedicle screws. Alignment of thefastening mechanism for the coupling mechanism with the longitudinalaxis of the pedicle screw allows the surgeon to more easily accomplishthe attachment of the coupling mechanism. In the embodiment of FIGS.28-31, the surgeon may insert a tightening instrument through thepercutaneous aperture in order to rotate the collet 614 into the splitring 620. A spinal fixation system including a fastening mechanism thisis substantially offset from the longitudinal axis of the pedicle screwpresents additional challenges for the surgeon because the fasteningmechanism may not be easily accessible through the aperture used inminimally invasive surgery.

Referring to FIG. 31, the passage in the body 612 that receives thepedicle screw 600 is sized to permit variations in the angle of thepedicle screw 600 with respect to the body 612. In a preferredembodiment, a screw angle of up to twenty degrees may be allowed by thebody 612 while still allowing the pedicle screw 600 to be positivelysecured to the fixation rod 602 by the coupling mechanism. Changes inthe orientation of the split ring 620 are permitted due to the curvedinterior profile of the passage in the body 612 matching the curvedexterior profile of the split ring 620, allowing the split ring 620 tobe positively secured at various angles with respect to the body 612.

The spinal fixation system embodiment depicted in FIGS. 28-31 may beinstalled into a spine in a similar fashion as shown with respect to theother spinal fixation system embodiments described herein.

Referring to FIGS. 32-36, a spinal fixation system according to anotherembodiment of the invention includes a pedicle screw 700, a couplingmechanism 702, and a fixation element, shown as fixation rod 722.Specifically referring to FIG. 33, a pedicle screw securing device,shown as collet 704, has a number of compressible arms 706 and includesan aperture sized to receive a post 716 of the pedicle screw 700. Areceiver includes a lower portion 708 and an upper portion 710, bothhaving apertures sized to fit over the collet 704. Further, the lowerportion 708 includes a fixation element receiving aperture, shown as rodaperture 712, and the upper portion 710 includes a fixation elementreceiving aperture, shown as rod aperture 714, both rod apertures 712,714 sized to receive fixation rod 722 (see FIG. 32). A fasteningmechanism, shown as nut 718, includes interior threads matching athreaded portion 720 of the collet 704.

Referring to FIGS. 34 and 35, the various components of the couplingmechanism 702 may be placed over the pedicle screw 700, using the post716 as a guide, prior to fastening the coupling mechanism 702 to thepedicle screw 700 and fixation rod 722. After the components of thecoupling mechanism 702 have been placed onto the pedicle screw 700, thenut 718 may be tightened onto the collet 704, drawing the compressiblearms 706 up into the lower portion 708 of the receiver, forcing the arms706 against the post 716, thereby securing the collet 704 at theselected height upon pedicle screw 700. The arms 706 have flat portionsor flats 724 that engage with the lower portion 708, preventing thecollet 704 from rotating along with the nut 718 during the tighteningprocess. Tightening of the nut 718 onto the threaded portion 720 alsosecures the coupling mechanism to the associated fixation rod 722because the compressible arms 706 pull the lower portion 708 into theupper portion 710, thereby shifting the alignment of the rod apertures712, 714 sufficiently to create an offsetting grip upon the fixation rod722, the receiver thereby functioning as a fixation element securingdevice.

Similar to certain other embodiments of the invention described herein,the embodiment shown in FIGS. 32-36 includes a coupling mechanism 702that may be secured to both a pedicle screw and a linking device via aone-step procedure, in this case the tightening of nut 718. Further,because the nut 718 is oriented along the longitudinal axis of pediclescrew 700, it may be accessed for fastening of the coupling mechanismthrough the small aperture used to insert the pedicle screw 700 inminimally invasive surgery. Further still, referring specifically toFIG. 36, the complimentary curved profiles of the lower portion 708,upper portion 710, and nut 718 allow for variability in the angle of thepedicle screw 700 within the receiver. The rounded portions of the arms706 between the flats 724 permit the collet 704 to be secured at anangle as shown in FIG. 36.

Referring to FIGS. 37-39, a spinal fixation system according to anotherembodiment of the invention includes a pedicle screw 800 and a couplingmechanism 802 intended to couple the pedicle screw 800 to a fixationelement or linking device such as a fixation rod (not shown). Thepedicle screw 800 includes a post 804 that extends through thecomponents of the coupling mechanism 802 including a receiver 806, acollar 812, a split ring 814, and a fastening mechanism, shown as nut816.

Referring to FIG. 38, the receiver 806 includes a receiver loop 808adapted to receive a fixation rod, and a pair of receiver arms 810, eachhaving an aperture sized to receive the collar 812 and post 804, andproviding enough space for the post 804 to extend through the receiver806 at an angle (see FIG. 39). The collar 812 includes a set of threadson the exterior thereof adapted to mate with corresponding internalthreads of the nut 816.

Referring to FIG. 39, the nut 816 has a spherical internal radius at anupper portion thereof allowing variability in the angle of the splitring 814 and the pedicle screw 800 within the coupling mechanism 802.Tightening of the nut 816 onto the collar 812 accomplishes twofunctions. First, the nut 816 forces the receiver arms 810 together,thereby securing the receiver loop 808 to a fixation rod (not shown)situated therein. Second, the nut 816 forces the split ring 814 downwardinto the collar 812, which collapses the split ring 814 onto the post804, thus securing the post 804 into place. Accordingly, the singleaction of tightening the nut 816 accomplishes the functions of securingthe pedicle screw 800 and the associated fixation element. The splitring 814 acts as a pedicle screw securing device and the loop 808 actsas a fixation element securing device.

Further referring to FIG. 39, the pedicle screw 800 is shown as securedby the coupling mechanism 802 at an angle relative to the collar 812. Asis apparent from FIG. 39, the angle is variable to permit a degree offlexibility in the attachment of the pedicle screw 800 to the couplingmechanism 802. As discussed above with respect to certain otherembodiments of the invention, the fastening device, shown as the nut816, is located on top of the pedicle screw 800, permitting access tothe fastening device through the percutaneous aperture used to insertthe pedicle screw 800 into the spine during a minimally invasivesurgical procedure.

Referring to FIGS. 40-42, in accordance with another embodiment of theinvention, a spinal fixation system includes a pedicle screw 900, afixation element, shown as a fixation rod 902, and a coupling mechanism,generally shown as coupling mechanism 904. The pedicle screw 900includes a threaded portion 906 and a post 908 that extends through aportion of the coupling mechanism 904.

Referring to FIG. 41, the coupling mechanism 904 includes a fixationelement securing device, shown as rod receiver 910, with an apertureconfigured to receive the fixation rod 902. The rod receiver 910includes a rod receiver loop 916 that encircles the fixation rod 902,and works in conjunction with a rod receiver base 918 that has a roundedchannel configured to receive the fixation rod 902. When the couplingmechanism 904 is secured, the rod receiver loop 916 and the rod receiverbase 918 combine to securely attach the coupling mechanism 904 to thefixation rod 902. A screw receiver 912 is configured similarly to therod receiver 910 and includes a screw receiver loop 920 and a screwreceiver base 922 that combine to serve as an attachment point for thepedicle screw 900. A screw receiver nut 924 has interior threads thatmate with exterior threads on the screw receiver loop 920 in order topull the screw receiver loop 920 into the screw receiver base 922 tofasten the pedicle screw 900 to the coupling mechanism 904 when thescrew receiver nut 924 is tightened. Likewise, a rod receiver nut 926contains interior threads that mate with exterior threads on the rodreceiver loop 916 in order to pull the rod receiver loop into the rodreceiver base 918, thus securing the fixation rod 902 to the couplingmechanism 904.

Referring to FIG. 42, the rod receiver components and the screw receivercomponents are attached to one another via a coupling protrusion 914extending from the screw receiver loop 920 into a receiving area definedby the rod receiver nut 926 and the rod receiver loop 916. In anexemplary embodiment, the coupling protrusion 914 is an integralextension of the screw receiver loop 920. Preferably, the couplingprotrusion 914 is shaped to permit variability in the angle ofattachment between the screw receiver components and the rod receivercomponents so that variability in the angle of the pedicle screw 900 ispermitted.

Further referring to FIGS. 40 and 42, the coupling mechanism 904components are secured to the pedicle screw 900 and fixation rod 902 byrotating the screw receiver nut 924 and rod receiver nut 926. In oneembodiment, the screw receiver nut 924 and the rod receiver nut 926 arerotated in opposite directions to secure the coupling mechanism 904.

The various spinal fixation or instrumentation systems described hereinas exemplary embodiments of the invention may be utilized in theperformance of spinal fusion procedures using a streamlined method thatis intended to simplify and shorten conventional spinal fusionprocedures. Prior to operating, imaging of the patient may be utilizedto determine the number of pedicle screws that will be linked togetheras part of the spinal fusion procedure. Further, an image guidancesystem may be utilized as part of the procedure to aid in the placementof the various components. In the case of an open procedure, an entrysite is created in the patient along the portion of the spine into whichthe pedicle screws will be inserted. In the case of a minimally invasiveprocedure, individual entry ports may be utilized for implantation ofindividual pedicle screws. The various embodiments of the inventiondescribed herein are particularly suited to a minimally invasiveapproach because the coupling components are placed upon the screw fromthe top, allowing insertion and connection of the components via thesmall percutaneous aperture created for the screw itself in contrast toother designs requiring the use of coupling components that are not inline with the longitudinal axis of the screw, which may require an openprocedure.

After creating the entry site and determining the point of insertion ofa pedicle screw, the pedicle screws described herein that are selfdrilling may be drilled directly through the pedicles and into thevertebra. Alternatively, if the drill system described herein isutilized, the drill may be inserted into the pedicle screw, using theholding device to hold the drill in place, and utilized to drill intothe pedicle simultaneously with the pedicle screw. Alternatively,conventional procedures may be utilized, including the pre-drilling andtapping of a hole in the pedicle, utilizing a Kirschner wire or guidewire as appropriate. The cannulated pedicle screws described herein areuseful for incorporating the drill or for the use of a guide wire asdesired by the surgeon.

After installation of the desired number of pedicle screws, the couplingmechanism is then utilized to connect the pedicle screws to a linkingdevice, such as a fixation rod or plate as shown and described hereinwith respect to several exemplary embodiments. In the case of aminimally invasive procedure, multiple drills may be utilized to aid inthe installation of the coupling components and the linking device maybe threaded beneath the patient's skin between the various pediclescrews that are being linked to each other.

After the pedicle screws have been placed into the vertebrae, thetransverse processes are decorticated prior to placing a bone graftmaterial to aid in the fusion of the adjacent vertebrae. Implantation ofthe bone graft material is typically done prior to the insertion of thefixation rod or plate to attach the pedicle screws together. The bonegraft implant shown in one embodiment in FIGS. 26 and 27 may be utilizedto insert the bone graft material. If a drill, such as drill 414, isutilized during the process of attaching the pedicle screws to thespine, the coupling components may be placed on to the shaft of thedrill to aid in the attachment of the fixation rod or plate. The drillsthat are utilized may then be removed from the pedicle screws. Theinstallation of all the components may be aided by a guidance systemsuch as a fluoronavigation system, especially in the case of minimallyinvasive procedures requiring image guidance where visual access isobscured.

While the detailed drawings and specific examples given herein describevarious exemplary embodiments, they serve the purpose of illustrationonly. It is to be understood that the invention is not limited in itsapplication to the details of construction and arrangements ofcomponents set forth in the preceding description or illustrated in thedrawings. It should be noted that the components and/or assemblies ofthe spinal fixation systems may be constructed from various materialsknown in the art. Further, while several examples show the invention inthe context of pedicle screw embodiments, the invention is alsoapplicable to other surgical procedures involving a bone anchoringelement or bone screw. Further, the order of performance of the methodsteps described with respect to spinal fixation procedures utilizing thevarious embodiments of the present invention may vary. Furthermore,other substitutions, modifications, changes and omissions may be made inthe design, operating conditions, and arrangements of the exemplaryembodiments without departing from the scope of the invention asexpressed in the appended claims.

What is claimed is:
 1. A spinal fixation system for fusing a firstvertebra and a second vertebra, the spinal fixation system comprising: aplurality of pedical screws configured to be inserted into the firstvertebra and second vertebra; a bone graft implant comprising: a meshbag defining a reservoir configured to contain bone graft material; afirst grommet to receive and couple to a first pedicle screw; a secondgrommet to receive and couple to a second pedicle screw; a linkingdevice to link the first pedicle screw to the second pedicle screw afirst coupling device to couple the linking device to the first pediclescrew; and a second coupling device to couple the linking device to thesecond pedicle screw.
 2. The spinal fixation system of claim 1, whereinthe coupling device comprises a receiver and a set screw.
 3. The spinalfixation system of claim 2, wherein the receiver comprises a pair ofsidewalls sized to receive the linking device and internal threads tothreadably receive the set screw.
 4. The spinal fixation system of claim1, wherein the coupling device comprises a receiver and a nut.
 5. Thespinal fixation system of claim 4, wherein the receiver comprises a pairof sidewalls sized to receive the linking device and external threads tothreadably engage the nut.
 6. The spinal fixation system of claim 1,wherein the mesh bag is a nylon mesh bag.
 7. The spinal fixation systemof claim 1, wherein the bone graft implant includes a pair of end capscoupled to the mesh bag.
 8. The spinal fixation system of claim 1,wherein the linking device is a fixation plate.
 9. The spinal fixationsystem of claim 1, wherein the linking device is a rod.
 10. A spinalfixation system for fusing a first vertebra and a second vertebra, thespinal fixation system comprising: a plurality of pedical screwsconfigured to be inserted into the first vertebra and second vertebra; abone graft implant comprising: a mesh bag defining a reservoirconfigured to contain bone graft material; a first grommet to receiveand couple to a first pedicle screw; a second grommet to receive andcouple to a second pedicle screw; a linking device to link the firstpedicle screw to the second pedicle screw a first coupling device tocouple the linking device to the first pedicle screw, the first couplingdevice having a first receiver and a first set screw, wherein the firstreceiver receives a first portion of the linking device and the firstset screw couples the linking device to the first receiver; and a secondcoupling device to couple the linking device to the second pediclescrew, the second coupling device having a second receiver and a secondset screw, wherein the second receiver receives a second portion of thelinking device and the second set screw couples the linking device tothe second receiver.
 11. The spinal fixation system of claim 10, whereinthe mesh bag is a nylon mesh bag, and wherein the bone graft implantincludes a pair of end caps coupled to the mesh bag.
 12. The spinalfixation system of claim 10, wherein the linking device is a fixationplate or a spinal rod.
 13. The spinal fixation system of claim 10,wherein the receiver comprises a pair of sidewalls sized to receive thelinking device and internal threads to threadably receive the set screw.14. A method for implanting a spinal fixation system for fusing a firstvertebra and a second vertebra, the spinal fixation system comprising:providing a first pedicle screw, a second pedicle screw, a linkingdevice to link the first pedicle screw to the second pedicle screw, afirst coupling device, and a second coupling device, and a bone graftimplant, the bone graft implant comprising a mesh bag defining areservoir containing bone graft material, a first grommet, and a secondgrommet; installing the first pedicle screw on the first vertebra andthe second pedicle screw on the second vertebra; coupling the bone graftimplant to the pedicle screws by inserting an end of the first pediclescrew through the first grommet and an end of the second pedicle screwthrough the second grommet; coupling the first coupling device to theend of the first pedicle screw; coupling the second coupling device tothe end of the second pedicle screw; coupling a first portion of thelinking device to the first coupling device; coupling a second portionof the linking device to the second coupling device.
 15. The method ofclaim 14, wherein the first coupling device comprises a first receiverand a first set screw, and wherein the step of coupling the firstportion of the linking device to the first coupling device comprisesinserting the first portion of the linking device between a pair of sidewalls on the first receiver and threading the first set screw intointernal threads on the pair of sidewalls.
 16. The method of claim 15,wherein the second coupling device comprises a second receiver and asecond set screw, and wherein the step of coupling the second portion ofthe linking device to the second coupling device comprises inserting thesecond portion of the linking device between a pair of side walls on thesecond receiver and threading the second set screw into internal threadson the pair of sidewalls.
 17. The method of claim 14, wherein the firstcoupling device comprises a first receiver and a first nut, and whereinthe step of coupling the first portion of the linking device to thefirst coupling device comprises inserting the first portion of thelinking device between a pair of side walls on the receiver andthreading the nut on external threads on the pair of sidewalls.
 18. Themethod of claim 17, wherein the second coupling device comprises asecond receiver and a second nut, and wherein the step of coupling thesecond portion of the linking device to the second coupling devicecomprises inserting the second portion of the linking device between apair of side walls on the receiver and threading the nut on externalthreads on the pair of sidewalls.
 19. The spinal fixation system ofclaim 14, wherein the linking device is a fixation plate.
 20. The spinalfixation system of claim 14, wherein the linking device is a rod.